Active drag-reduction system and a method of reducing drag experienced by a vehicle

ABSTRACT

An active drag-reduction system has first  22  and second  24  fluid outlets located on a vehicle  10  adjacent to a low pressure (drag) region  12,  wherein fluid ejected from the second fluid outlet  24  is at a higher pressure/ejection velocity than from the first fluid outlet  22.  Turbulent and/or low pressure regions adjacent to vehicles are not uniform, but rather have a varying intensity. For instance, the centre of a region may have a lower pressure and/or more turbulent nature than the periphery of the region. The system injects relatively higher pressure air or relatively higher speed air into the relatively lower pressure/more turbulent part of the low pressure/turbulent region, and relatively lower pressure air or relatively lower speed air into the relatively higher pressure/less turbulent part of the low pressure/turbulent region, compared to each other.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.16/293,619, filed Mar. 5, 2019, which claims priority under 35 U.S.C. §120 to, and is a continuation of, International ApplicationPCT/GB2016/052729, filed Sep. 5, 2016 and designating the US. Theseapplications are incorporated by reference herein in their entireties.

BACKGROUND Field

The present invention relates generally to an active drag-reductionsystem for vehicles and a method of reducing drag experienced byvehicles moving at speed and finds particular, although not exclusive,utility when applied to aeroplanes, aerofoils (including those used inwind turbines), automobiles, cars, lorries, trains and motorbikes.

Drag (also referred to as fluid resistance) experienced by movingvehicles of various different types comprises three main components:skin friction encountered in laminar flow, which is approximatelyproportional to the velocity of the vehicle in question; form dragencountered in turbulent flow, which is approximately proportional tothe square of the velocity of the vehicle; and vortex drag, for examplewingtip, trailing or lift-induced vortices, which are circular patternsof rotating air left behind a wing as it generates lift, in particularat the wing tips, but also at any point on the wing where the liftvaries span-wise, at the edge of flap devices, or at other abruptchanges in wing planform.

SUMMARY

It is desirable to minimise all forms of trailing vortices from a movingvehicle, whether they are from turbulent form drag of a vehicle or fromvortex drag, for instance by ensuring that the maximum proportion of thedrag is due to skin friction. Turbulent flow around a vehicle occursduring flow separation, when a low pressure and/or turbulent vortexregion is formed (for instance, behind the vehicle), characteristic of ahigh Reynolds number in which turbulent flow dominates over laminarflow. In some vehicles multiple smaller vortices may form around thevehicle; in other vehicles, relatively large vortices may be formed.Elimination of these through shaping of bodywork of vehicles is commonpractice to increase efficiency of the vehicle.

It is also desirable to minimise vortex drag in particular, as wingtipvortices on aircraft can persist for relatively long times (of the orderof several minutes after the passage of an aircraft) which can causedanger to other aircraft, in particular around airfields where time mustbe left between subsequent take-offs and/or landings on a given runwayfor such vortices to dissipate.

According to a first aspect of the present invention, there is providedan active drag-reduction system for a vehicle in which at least oneturbulent and/or low-pressure region is formed adjacent to the vehiclewhen moving at a speed above a predetermined threshold speed, the activedrag-reduction system configured to reduce the at least one turbulentand/or low-pressure region when activated, the active drag-reductionsystem comprising: at least one convergent propelling nozzle locatedadjacent to a boundary of the at least one region; at least onedivergent propelling nozzle located adjacent to the at least one regionand spaced from the boundary of the at least one region, the at leastone divergent propelling nozzle arranged to eject fluid substantiallytoward an interior of the at least one region; and a device forproviding gas to each of the at least one convergent and divergentpropelling nozzles for expulsion into the at least one region.

According to a second aspect of the present invention, there is providedan active drag-reduction system for a vehicle in which at least oneturbulent and/or low-pressure region is formed adjacent to the vehiclewhen moving at a speed above a predetermined threshold speed, the activedrag-reduction system configured to reduce the at least one turbulentand/or low-pressure region when activated, the active drag-reductionsystem comprising: at least one propelling nozzle located adjacent tothe at least one region and arranged to eject fluid substantially towardan interior of the at least one region; and a device for providing gasto the at least one nozzle for expulsion into the at least one region;wherein the at least one propelling nozzle comprises a tip ringsupersonic nozzle and/or elliptic sharp tipped shallow lobed nozzle.

Turbulent and/or low pressure regions adjacent to vehicles are notuniform, but rather have a varying intensity. For instance, the centreof a region may have a lower pressure and/or more turbulent nature thanthe periphery of the region. In this way, therefore, the presentinvention allows the system of the present invention to injectrelatively higher pressure air (or relatively higher speed air) into therelatively lower pressure/more turbulent part of the lowpressure/turbulent region, and relatively lower pressure air (orrelatively lower speed air) into the relatively higher pressure/lessturbulent part of the low pressure/turbulent region, compared to eachother.

The at least one first and second fluid outlets may be configured toencourage laminar flow adjacent to a surface of the vehicle on whichthey are located.

In particular, the fluid ejected into the at least one region may act tofill the low-pressure and/or turbulent region, and may also act to drawadjacent laminar flow toward it (e.g. in accordance to Bernoulli'sprinciple).

The at least one first fluid outlet may be located on the vehicleadjacent to a perimeter of the at least one region.

The at least one first fluid outlet may be arranged to eject fluidsubstantially parallel to a periphery of (e.g. tangentially to) the atleast one region. That is, the at least one fluid outlet may be arrangedsuch that, prior to activation of the system, fluid ejected therefromwould be directed substantially parallel to the periphery of the atleast one region; however, subsequent to activation of the system, thesize and shape of the region may be modified such that fluid ejectedtherefrom may be directed in a direction substantially non-parallel tothe periphery of the at least one region.

The at least one second fluid outlet may be arranged to eject fluidsubstantially toward an interior of the at least one region. Forinstance, the at least one second fluid outlet may be located on anaircraft wing to direct relatively high pressure or fast air into thecentre of a wing-tip vortex, and/or the at least one first fluid outletmay be located on an aircraft wing to direct relatively low pressure orslow air along the bounding surface of the wing-tip vortex.

Alternatively of additionally, a plurality of second fluid outlets maybe located along a trailing edge of an aerofoil. Optionally, a pluralityof first fluid outlets may be arranged substantially above and/or belowthe plurality of second fluid outlets.

The at least one first fluid outlet may comprise only one, two, three,four, five or more first fluid outlets. For instance, the first fluidoutlets may be arranged in a row along an edge of the vehicle. Fluidejected therefrom may be ejected at a speed sufficient to encourage theCoanda effect in fluid passing over that edge; that is, laminar flow maybe encouraged around the edge.

The at least one second fluid outlet may comprise only one, two, three,four, five or more first fluid outlets. For instance, the second fluidoutlets may be arranged in a row and/or an array spaced from the edge ofthe vehicle.

The system may further comprise at least one third fluid outlet locatedon the vehicle adjacent to the at least one region and spaced from theat least one first fluid outlet and the at least one second fluidoutlet; and the fluid supply system may be configured to: provide fluidat a third pressure and/or third ejection velocity to the at least onethird fluid outlet, wherein the third pressure and/or third ejectionvelocity is greater than the first pressure and/or first ejectionvelocity, and less than the second pressure and/or first ejectionvelocity, respectively. The system may further comprise at least onefourth, fifth, etc. fluid outlet similar, mutatis mutandis, to the atleast one third fluid outlet.

The first pressure and/or first ejection velocity may be between 4% and35% of the second pressure and/or second ejection velocity, inparticular between 5% and 20%, more particularly between 6% and 10%, forinstance approximately 6%, 7% or 8%.

Similarly, the third pressure and/or third ejection velocity may bebetween 8% and 40% of the second pressure and/or second ejectionvelocity, in particular between 10% and 35%, more particularly between12% and 20%, for instance approximately 12%, 15% or 18%.

In one arrangement, a first row of first fluid outlets is providedimmediately below a spoiler of a car, a second row of second fluidoutlets is provided immediately above a rear bumper/fender of a car, and(optionally) a third row of third fluid outlets is provided between thefirst row and the second row (for instance approximately half-waybetween).

The system may be configured to supply relatively high temperature fluidto the at least one first and/or second fluid outlets. The relativelyhigh temperature fluid may have a temperature of between 70 and 130degrees centigrade, in particular between 90 and 120 degrees centigrade,more particularly approximately 110 degrees centigrade.

The system may be configured to supply relatively low temperature gas tothe at least one second and/or first fluid outlets. The relatively lowtemperature gas may have a temperature of between −50 and 10 degreescentigrade, in particular between −40 and −10 degrees centigrade, moreparticularly approximately −30 degrees centigrade.

The relatively high and the relatively low temperatures referred to maybe relative to one another, and/or relative to ambient temperatureand/or approximately 20 to 30 degrees centigrade. That is, the systemmay be configured to supply fluid to the first fluid outlet(s) at atemperature substantially higher or lower than to the second fluidoutlet(s).

The system may heat and/or cool gas to provide the relatively high andrelatively low temperature gas by any conventional means, for instance,electrical heating, via heat form a coolant system of an engine withinthe vehicle, from a heat exchanger with for instance exhaust gases, fromthe heat of compression of gas, from cooling due to expansion of thegas, from a heat exchanger with ambient air, from a refrigerationsystem, from a liquid nitrogen storage system, or due to passage down acorrugated pipe/tube or due to passage down a pipe/tube having an unevenand/or non-smooth interior.

The system may comprise a vortex tube configured to split gas into arelatively high temperature stream and a relatively low temperaturestream, and may be configured to convey the high temperature stream tothe at least one first and/or second fluid outlets and the lowtemperature stream to the at least one second and/or first fluidoutlets, respectively.

The vortex tube may be a Ranque-Hilsch vortex tube, for instance of anyknown configuration. In particular, the vortex tube may comprise a swirlchamber and/or a conical nozzle, as is well known in the art.

The system may comprise a pump (e.g. an air pump as described below) acompressor (e.g. an air compressor as described below) or any othersystem for providing fluid, gas and/or air to the region via theoutlets, preferably in a compressed form compared to ambient; this willbe referred to herein as ‘compressed air’, but is intended to cover allstated possibilities unless otherwise stated. A pump may provide fluiddirectly to an outlet, or may provide fluid to a vortex tube that maythen provide a relatively hot gas stream to one outlet and a relativecold gas stream to another outlet. The pump may be in the form of acompressed air pump, or may be a compressor located at an engine inlet(for instance as is present in a turbo charger), where compressed airmay be bled off before introduction into the engine.

The exhaust of an engine (e.g. an internal combustion engine) mayprovide gas (e.g. exhaust gas) directly to a nozzle, or may provide gasto a vortex tube that may then provide a relatively hot gas stream toone nozzle and a relatively cold gas stream to another nozzle.

In some embodiments, gas from a pump may be combined with bled-offand/or exhaust gas before being provided to a nozzle and/or a vortextube in the manner described above. In alternative embodiments,relatively hot or cold gas streams from a vortex tube may be combinedwith bled-off and/or exhaust gas before being provided to a nozzle. Inthis way, noise due to the turbulent motion of the bled-off and/orexhaust gas can be reduced, thereby reducing overall engine noise. Inparticular, reducing the temperature of the exhaust gas reduces thesound energy carried with the exhaust gas. Combining the gas from thepump and/or vortex tube may be by mixing, for instance by providing theexhaust gas into gas flow (or vice versa) via a coaxial pipe arrangementand/or via a mixer nozzle, for instance a spray nozzle, a duplex nozzleand/or a sewer nozzle. The mixer nozzle may have a primary outlet thatprovides gas flow therethrough in a substantially continuous direction,and at least one secondary outlets that provide gas flow therethrough ina substantially deflected direction. The deflected direction may bebetween 10 and 170 degrees, for instance, approximately 15 degrees, 30degrees, 70 degrees, 90 degrees, 110 degrees or 130 degrees.

In one embodiment, gas from the pump is split into a first stream thatis directed to the vortex tube and a second stream that is delivered forcombination with exhaust gas.

The gas after combination may have a relatively high or a relatively lowtemperature, and may be directed to an appropriate portion of the regionas discussed above. Preferably, the combined gas has a relatively lowtemperature and is directed to a nozzle directed towards an interiorportion of the region, spaced from a boundary of the region.

In some arrangements, the system may be reversed such that relativelyhigh temperature air is expelled into a high pressure region in front ofthe vehicle, which may be present due to ram forces. The injectedrelatively high temperature air may warm the high pressure region,encouraging it to expand and dissipate; in any event, however, thehigher temperature air is less dense than the ambient air. The lessdense air replaces the ambient air in the high pressure region, and dueto the lower density drag is reduced. In particular, in some specificarrangements, outlets may be directed toward relatively high pressureregions adjacent to the vehicle. In effect, this system may act as avirtual and/or invisible air splitter, for example serving to increasethe amount of downforce at the front of a car on to which it is applied.An incoming airstream may be brought to stagnation by the expelled air,causing an area of high pressure. Below, air is redirected away from thestagnation zone and is accelerated, causing a pressure to drop, therebycreating downforce.

A further optional alternative would be to configure the system to blowrelatively cool air (compared to ambient) over the surface of anaerofoil, for example during take-off of an aircraft. The cooler air isdenser than ambient air, and therefore the density of air is increasedlocally around the wing. Lift generated by an aerofoil is proportionalto the density of the air in which it acts; therefore, in this manner,more lift can be generated. This may be of particular use in hotenvironments where take-off from a ground-level runway can be severelyimpacted by high temperatures. Such relatively cool air may be blownover the surface of the aerofoil by a plurality of holes in the surfaceof the aerofoil, in particular on the high pressure side of the aerofoil(e.g. beneath an aircraft wing, or above an aerofoil wing on a car).Similarly, relative warm air (compared to ambient and/or the relativelycool air) may be blown over the surface of the aerofoil, in particularon the low pressure side of the aerofoil (e.g. beneath an aircraft wing,or above an aerofoil wing on a car). These modifications may inparticular be used in relation to wind turbine blades.

The fluid outlets may comprise at least one propelling nozzle. Thepropelling nozzle may be located at an exhaust and/or air outlet. Thegas referred to may be air, atmospheric air, engine exhaust, othergases, or a combination thereof. The region may be behind the vehicle,located on a wing and/or aerofoil of a vehicle, behind the cabin of alorry, or in any other low pressure region adjacent to the vehicle.

The propelling nozzle may comprise a convergent and/or a divergentpropelling nozzle. The propelling nozzle may have a pressure ratiodefined as the outlet pressure divided by the inlet pressure. In thecase of a convergent nozzle, if the nozzle pressure ratio is above acritical value (typically between approximately 1.6:1 to 2:1, e.g. about1.8:1), the nozzle will choke, resulting in some expansion to ambientpressure taking place downstream of the nozzle throat (i.e. the portionof the nozzle having the smallest cross-sectional flow area); that is,in the jet wake. In this way, the imbalance between the throat staticpressure and ambient pressure generates some (pressure) thrust.

The propelling nozzle may be, for example, a convergent-divergentpropelling nozzle, which may be a form of divergent propelling nozzle.In a convergent-divergent nozzle, expansion occurring downstream of theconvergent nozzle section acts against the inside of the divergentnozzle portion.

The propelling nozzle may comprise an ejector nozzle. The propellingnozzle may comprise a divergent propelling nozzle. Alternatively oradditionally, the propelling nozzle may comprise a convergent propellingnozzle, for instance such that the convergent propelling nozzle isconfigured to produce a relatively high velocity jet, for instance whencompared to the velocity of gas introduced to the convergent propellingnozzle and/or the velocity of gas expelled from the divergent propellingnozzle.

The at least one first fluid outlet may be located adjacent to aboundary of the region. That is, the at least one first fluid outlet maybe located to direct a jet of fluid into a boundary/boundary-layer ofthe region. The region may be a turbulent boundary layer, and theboundary of the region may be the extent of the boundary layer. The atleast one first fluid outlet may be located such that the extent of theboundary layer is reduced.

A high velocity jet may eliminate the region boundary/vortexboundary/eddy line by inducing the gas therein to equalise speed withgas outside the region.

The divergent nozzle may be configured to produce a relatively highpressure jet, for instance when compared to the pressure of gasintroduced to the nozzle and/or the pressure of gas expelled from theconvergent propelling nozzle.

The at least one second fluid outlet may be spaced from a boundary ofthe region. That is, the at least one second fluid outlet may be locatedto direct a jet of gas into the region, for instance into a central partof the region, a part of the region spaced from aboundary/boundary-layer of the region. Where ‘spaced’ with reference tothe location of the divergent nozzle may be viewed as a comparative termto ‘adjacent to’ with reference to the location of the convergentnozzle.

A high pressure jet may act to remove the low pressure region byexpanding into said region.

The propelling nozzle may accelerate the available gas to subsonic,sonic, or supersonic velocities. The internal shape may be convergent orconvergent-divergent. The propelling nozzle may have a fixed geometry,or they may have variable (i.e. controllable) geometry to give differentexit areas to control the characteristics of the propelling jet. Thepropelling nozzle may be an ejector nozzle; however, other nozzleconfigurations are contemplated.

The propelling nozzle may be a supersonic ejector, for instance aconical nozzle; however, a tip ring nozzle, or an elliptic sharp tippedshallow (ESTS) lobed nozzle, as described in “Novel supersonic nozzlesfor mixing enhancement in supersonic ejectors”, Srisha M. V. Raoa & G.Jagadeesh, Applied Thermal Engineering, Volume 71, Issue 1, 5 Oct. 2014,Pages 62-71, the contents of which is incorporated by reference hereinin its entirety. Such preferred arrangements provide enhance mixing overthat evident from a conical nozzle, for example a 30% increase inentrainment of secondary flow, and also provide a reduction incompression ratio of between 15% and 50%. In a conventional cone-shapednozzle, the jet is ejected with massive momentum, carrying huge energyand creating noise. However, in the preferred nozzle configurations, thejet is spread and assimilated into the cold atmosphere more quickly,making the jet quieter and improving the ‘push’ provided by thepropelling nozzle. Potentially, this could lead to a reduction in soundof between 25% and 35%.

The tip ring nozzle may comprise a divergent nozzle having a circularring protruding at the exit of a conical nozzle. In particular, the tipring nozzle may comprise a convergent-divergent nozzle, at the internalperiphery of the outlet of the divergent nozzle section there may beprovided an annular protrusion extending into the flow, the protrusionhaving a form that may be substantially ring-like (e.g. donut-shape ortoroidal), and extending into the flow from the interior of thedivergent nozzle section by approximately 5% of the radius of thedivergent nozzle section outlet (e.g. between 2% and 10%, in particularbetween 4% and 8%, for instance 5 to 7%.

The elliptic sharp tipped shallow (ESTS) lobed nozzle may have ellipticlobes with relatively sharp tips (e.g. forming a cusp between thelobes), the tips protruding only a relatively short distance into theflow). In particular, they may project between approximately 5% and 20%of the radius of the nozzle outlet, more particularly betweenapproximately 7% and 15%, for example 10%. The ESTS lobed nozzle maycomprise a conventional lobed nozzle modified to have lobes with anelliptical cross-section projecting radially outward, and with cuspsdefining the join between adjacent elliptical regions, the cuspsprojecting inwardly from the interior wall of the divergent nozzlesection by between approximately 5% and 20% the radius. In somearrangements, substantially the entire divergent nozzle section has sucha cross-sectional form. In preferred embodiments, the nozzle maycomprise four lobes; however, three, five, six or more lobes are alsoenvisaged. The ESTS lobed nozzle may comprise a convergent-divergentnozzle.

The propelling nozzle may comprise aluminium alloy.

According to a third aspect of the invention, there is provided a methodof reducing vehicular drag, the method comprising the steps of:providing a system according to the first or second aspect; andexpelling gas from the at least one nozzle into an interior of the atleast one region.

Alternators in motor vehicles are typically driven by the crankshaft,which converts the reciprocal motion of a piston into circular movement.Some early model vehicles used a separate drive belt from the crankshaftpulley to the alternator pulley, but most cars today have a serpentinebelt, or one belt that drives all components that rely on crankshaftpower. However, as more power is drawn from the crankshaft to operatesuch ‘accessory components’, the net or effective power output of theengine decreases for producing useful work such as for locomotion.

According to a fourth aspect of the present invention, there is provideda vehicle configured such that, when moving at a speed above apredetermined threshold speed, at least one turbulent and/orlow-pressure region is formed adjacent to the vehicle, the vehiclecomprising an engine system comprising: an internal combustion enginehaving an intake and an exhaust; a turbine connected to the exhaust suchthat the turbine rotates in response to receiving exhaust gases from theengine; an alternator connected to the turbine such that the alternatorgenerates electrical power in response to rotation of the turbine; andan exhaust outlet connected to the turbine, for removing exhaust gasesthat have been used to rotate the turbine, the exhaust outlet comprisinga propelling nozzle located on a rear of the vehicle such that theexhaust gases are expelled substantially toward an interior of aturbulent and/or low-pressure region behind the vehicle; wherein theexhaust provides gas directly to the nozzle.

In this way, the engine is not required to drive the alternatordirectly, for instance with a crankshaft, thus the alternator does notdraw power from the engine, which would otherwise reduce the poweravailable from the engine for locomotion. In contrast, according to thepresent invention, the alternator is driven by the exhaust gases leavingthe engine, which allows all power generated by the engine (and fed intothe crankshaft) to be used for primary purposes, such as locomotion.Hence, for a given desired power output of an engine, a smaller(therefore lighter), and potentially more efficient, engine may be used,as the net power output will be higher than that of a conventionalengine in which the alternator is connected to the crankshaft.

Exhaust gases from an internal combustion engine are typically at highertemperature and/or pressure than ambient. The turbine may be configuredto operate as a turboexpander, such that the relatively high-pressureexhaust gas is expanded to produce work (i.e. to rotate the turbine). Indoing so, thermal energy from the exhaust gas is extracted and convertedto rotational energy of the turbine; that is, as the exhaust gas expandsthrough the turboexpander, the temperature of the exhaust gas drops asheat energy is converted to rotational kinetic energy of the turbine(e.g. rotation of an impeller or rotor).

The turbine may be any form of known turbine. The turbine may comprisean impulse type turbine, for instance a Pelton wheel turbine, forextracting energy from the impulse of the moving fluid. Alternatively oradditionally, the turbine may be a reaction type turbine. The turbinemay have a multi-blade construction. For instance, the turbine maycomprise a double-blade turbine. The turbine may have only one turbinestage, or a plurality of turbine stages (e.g. two stages). Each turbinestage may be of a similar type, or may differ from some or all otherstages. The turbine or impeller may be, for instance, an aluminiumalloy, that may be selected to resist the high temperature and pressuresencountered within the fluid flow; however, other constructions are alsocontemplated, such as ceramics and/or other metals. The turbine maycomprise bearings (for instance low-friction bearings, such as polymerbearings) upon which an impeller or rotor rotates.

In addition, exhaust gases from an internal combustion engine typicallyhave a relatively high velocity; that is exhaust gases from the internalcombustion engine (expelled from the cylinder) are not usually vented toambient immediately, but are rather conveyed along an exhaust pipe. Thepressure of exhaust gases from the cylinder pushes exhaust gasses withinthe pipe, such that the exhaust gases obtain a velocity through thepipe. In the present invention, the turbine may be arranged to receivesuch exhaust gases having a velocity, and may be configured to extractkinetic energy due to their velocity. In this way, a ram pressure due toa velocity of the exhaust gases relative to the turbine may be presenton the turbine, and the turbine may use this ram pressure to extractkinetic energy from the flowing exhaust gases, and convert it intorotational kinetic energy of the turbine.

A reduction in pressure and/or velocity of the exhaust gases across theturbine may act to reduce the amount of sound energy in the exhaustgases. In particular, the turbine may be configured to convert somesound energy in the exhaust gases into kinetic energy. The turbine maybe configured or further configured to dampen incoherent vibrationswithin the exhaust gases, thereby reducing volume of any sound from theexhaust gases.

The turbine may be configured to rotate at a predetermined RPM inresponse to receiving exhaust gas from the engine, for instance aboveapproximately 2000 rpm, between approximately 2500 and 8000, inparticular between approximately 3000 and 6000 rpm, more particularlybetween approximately 3500 and 5000 rpm (e.g. approximately 4000 or 4500rpm). In this way, no gearbox is required between the turbine and thealternator to generate desired electrical power at the alternator.Further, as the alternator is connected to the turbine rather than acrankshaft of the engine, no gearing is required between the crankshaftand the alternator, thus allowing smaller and lighter overall enginesize.

Configuring the turbine to rotate at a predetermined RPM may includeusing a wastegate on the exhaust, to limit the upper rotational speed ofthe turbine by removing a portion of the exhaust gases from the exhaustbefore interaction with the turbine, and/or selecting a suitable turbineblade configuration (including angle of attack), using conventionalmethods.

The alternator may be connected to the turbine in any manner known tothose skilled in the art similar to the manner in which alternators areconventionally connected to a crankshaft of an engine, for instance bybelt, chain or gears.

The alternator may be spaced from the engine, for instance by more than25 cm, 50 cm, 1 m, 2 m, etc. In this way, performance and handling of avehicle may be improved by selecting appropriate location (e.g. weightdistribution) of engine system components (such as the engine and thealternator). The turbine may be connected to (e.g. in fluidcommunication with) the exhaust by an exhaust pipe. In particular, theturbine may be located at substantially any location along an exhaustpipe from the engine, allowing the alternator, and optionally thebattery, to be similarly located.

The turbine may be connected to at least one further piece of accessoryequipment, including a water pump, an air conditioning compressor,and/or an air pump.

The air pump may be a rotary vane pump, reciprocating (piston)compressor, or any other suitable form of pump or compressor. The airpump may pressurise air up to 600 kpa, 700 kpa, 800 kpa, 850 kpa, 900kpa or 1 Mpa. The air pump may be constructed from aluminium alloy orany other suitable metal, ceramic, or carbon fibre. The air pump maycomprise a non-return valve. The air pump may take in ambient air at apump inlet and expel pressurised air to the exhaust outlet, or adistinct air outlet, for instance to a propelling nozzle, as describedabove. In this way, air may be compressed and sent to the exhaust/airoutlet to eliminate vortices behind a vehicle in which the engine systemis located.

In some embodiments, the air outlet may be connectable to pneumatictyres of a vehicle in which the engine is located, such that inflationof the tyres may be effected. In particular, a hose may be connectablebetween the air outlet and the tyres, for instance manually. In somearrangements, the air outlet may be permanently connected to the tyres,and air flow into the tyres may be controllable by a selection switch(which may be manually operable, mechanical, electronic and/orautomatic). In some embodiments, the hose may be connectable directly toa propelling nozzle, as described above, for instance via a push-fitconnector, screw connector, expanding collar/collet connector or similarconnection. In further embodiments, the air pump may be controllable tosupply variable air pressures depending on the desired function; forinstance, to inflate tyres, to eliminate vortices behind the vehicleand/or to supply air to the engine air intake.

The turbine may be connected to a compressor for delivering compressedgas to the intake, in the manner of a conventional turbocharger. Inparticular, the compressor may comprise the at least one further pieceof accessory equipment, specifically the air pump. The compressor/airpump may have a dual function; specifically, to operate a turbochargerand/or an air outlet. The dual function may comprise a toggle switch forselecting between respective air and/or turbocharger functions, and/orbalancing a proportion of pressurised air to be supplied respectively tothe turbocharger and/or air outlet.

A metering valve may be provided between the compressor and the intake,to regulate the pressure of gas being provided to the intake. In thisway, optimum operation of the engine may be achieved. The metering valvemay be computer controlled; however, in alternative embodiments, themetering valve may incorporate some other form of feedback system, forinstance a pressure regulated feedback system. The metering valve maycomprise a mechanism for diverting a portion of gas from the compressordirectly to the exhaust and/or exhaust outlet (i.e. bypassing theengine), which may be enabled in a similar manner to a conventionalwastegate.

A pressure relief valve may be incorporated within the system to reducea level of pressure in excess of a predetermined threshold pressure. Thepredetermined threshold pressure may be adjustable such that thepressure relief valve may be an adjustable pressure relief valve. Suchpressure relief valves may be located at various points throughout thesystem, for instance immediately before the compressor, immediatelyafter the compressor, immediately before the intake, between thecompressor and the intake, immediately after the exhaust, immediatelybefore the turbine, between the exhaust and the turbine, immediatelyafter the turbine, immediately before the exhaust outlet, and/or betweenthe turbine and the exhaust outlet.

After passing through the turbine, exhaust gases may be delivered to anexhaust outlet, which may be located on a rear of a vehicle in which theengine system is incorporated. A check valve may be provided between theturbine and the outlet, in order to regulate the amount of exhaust gaspassed to the outlet, and may act as a downstream restrictor that may becontrolled to optimise function of the turbine.

In particular, the exhaust/air outlet may comprise a propelling nozzleas described above. For instance, exhaust gasses (or gasses from the airoutlet) are converted into a relatively high speed propelling jet by thepropelling nozzle. The propelling nozzle may be configured to optimiseoperation of the turbine by functioning as a downstream restrictor. Avehicle incorporating the engine system described above may furthercomprise an exhaust outlet connected to the turbine, for removingexhaust gases that have been used to rotate the turbine. The exhaustoutlet may be located on a rear of the vehicle such that the exhaustgases are expelled into a turbulent and/or low-pressure region behindthe vehicle. In this way, the effect of form drag (due to the shape ofthe vehicle) can be minimised, by filling the turbulent and/orlow-pressure region behind the vehicle with exhaust gases. Any airincident on the front of a vehicle that is taken into the engine (e.g.from a radiator grill) may be expelled immediately behind the vehicle,thereby reducing drag by means of symmetry.

According to a fifth aspect of the present invention, there is provideda method of reducing vehicular drag, the method comprising the steps of:providing a vehicle according to the fourth aspect; and expelling gasfrom the at least one nozzle substantially toward an interior of the atleast one region.

According to a sixth aspect of the present invention, there is providedan engine system of a vehicle, the engine system comprising: an internalcombustion engine having an intake and an exhaust; a Pelton wheelturbine of the impulse type connected to the exhaust such that theturbine rotates in response to receiving exhaust gases from the engine;an exhaust outlet to which exhaust gases are delivered after passingthrough the turbine; an alternator connected to the turbine such thatthe alternator generates electrical power in response to rotation of theturbine; a propelling nozzle distinct from the exhaust outlet, thepropelling nozzle arranged to eject fluid substantially toward aninterior of a turbulent and/or low-pressure region behind the vehicle;an air pump connected to the turbine, the air pump configured to take inambient air at a pump inlet and expel pressurised air to the propellingnozzle; and the propelling nozzle configured such that gasses from thepropelling nozzle are converted into a higher speed propelling jet,relative to the speed of the expelled pressurised air from the air pump.

According to a sixth aspect of the present invention, there is provideda method of using energy in exhaust gas from an internal combustionengine, the method comprising the steps of: providing an internalcombustion engine of a vehicle having an intake and an exhaust;providing a Pelton wheel turbine of the impulse type connected to theexhaust; rotating the turbine in response to receiving exhaust gasesfrom the engine; delivering the exhaust gases to an exhaust outlet afterpassing through the turbine; providing an alternator connected to theturbine; generating electrical power with the alternator in response torotation of the turbine; providing an air pump connected to the turbine;taking in ambient air at a pump inlet of the air pump; providing apropelling nozzle distinct from the exhaust outlet, the propellingnozzle arranged to eject fluid substantially toward an interior of aturbulent and/or low-pressure region behind the vehicle; and expellingpressurised air from the air pump to the propelling nozzle; andconverting the expelled pressurised air from the air pump with thepropelling nozzle into a higher speed propelling jet, relative to thespeed of the expelled pressurised air from the air pump.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other characteristics, features and advantages of thepresent invention will become apparent from the following detaileddescription, taken in conjunction with the accompanying drawings, whichillustrate, by way of example, the principles of the invention. Thisdescription is given for the sake of example only, without limiting thescope of the invention. The reference figures quoted below refer to theattached drawings.

FIG. 1 is a schematic representation of airflow around the rear of aconventional automobile.

FIG. 2 is a schematic representation of airflow around the rear of theautomobile of FIG. 1 incorporating an active drag-reduction system.

FIG. 3 is a schematic representation of an articulated lorryincorporating an embodiment of the present invention.

FIG. 4 is a longitudinal cross section through an outlet of a tip ringnozzle.

FIG. 5 is an end on (axial) view of an outlet of an elliptic sharptipped shallow lobed nozzle.

FIG. 6 is schematic representation of a typical prior art internalcombustion engine and alternator system.

FIG. 7 is a schematic representation of a first engine systemarrangement.

FIG. 8 is a schematic representation of a second engine systemarrangement.

FIG. 9 is a schematic representation of a third engine systemarrangement.

FIG. 10 is a schematic representation of a fourth engine systemarrangement.

FIG. 11 is a schematic representation of a fifth engine systemarrangement.

FIG. 12 is a schematic representation of a sixth engine systemarrangement

DETAILED DESCRIPTION

The present invention will be described with respect to certain drawingsbut the invention is not limited thereto but only by the claims. Thedrawings described are only schematic and are non-limiting. Each drawingmay not include all of the features of the invention and thereforeshould not necessarily be considered to be an embodiment of theinvention. In the drawings, the size of some of the elements may beexaggerated and not drawn to scale for illustrative purposes. Thedimensions and the relative dimensions do not correspond to actualreductions to practice of the invention.

Furthermore, the terms first, second, third and the like in thedescription and in the claims, are used for distinguishing betweensimilar elements and not necessarily for describing a sequence, eithertemporally, spatially, in ranking or in any other manner. It is to beunderstood that the terms so used are interchangeable under appropriatecircumstances and that operation is capable in other sequences thandescribed or illustrated herein.

Moreover, the terms top, bottom, over, under and the like in thedescription and the claims are used for descriptive purposes and notnecessarily for describing relative positions. It is to be understoodthat the terms so used are interchangeable under appropriatecircumstances and that operation is capable in other orientations thandescribed or illustrated herein.

It is to be noticed that the term “comprising”, used in the claims,should not be interpreted as being restricted to the means listedthereafter; it does not exclude other elements or steps. It is thus tobe interpreted as specifying the presence of the stated features,integers, steps or components as referred to, but does not preclude thepresence or addition of one or more other features, integers, steps orcomponents, or groups thereof. Thus, the scope of the expression “adevice comprising means A and B” should not be limited to devicesconsisting only of components A and B. It means that with respect to thepresent invention, the only relevant components of the device are A andB.

Similarly, it is to be noticed that the term “connected”, used in thedescription, should not be interpreted as being restricted to directconnections only. Thus, the scope of the expression “a device Aconnected to a device B” should not be limited to devices or systemswherein an output of device A is directly connected to an input ofdevice B. It means that there exists a path between an output of A andan input of B which may be a path including other devices or means.“Connected” may mean that two or more elements are either in directphysical or electrical contact, or that two or more elements are not indirect contact with each other but yet still co-operate or interact witheach other.

Reference throughout this specification to “an embodiment” or “anaspect” means that a particular feature, structure or characteristicdescribed in connection with the embodiment or aspect is included in atleast one embodiment or aspect of the present invention. Thus,appearances of the phrases “in one embodiment”, “in an embodiment”, or“in an aspect” in various places throughout this specification are notnecessarily all referring to the same embodiment or aspect, but mayrefer to different embodiments or aspects. Furthermore, the particularfeatures, structures or characteristics of any embodiment or aspect ofthe invention may be combined in any suitable manner, as would beapparent to one of ordinary skill in the art from this disclosure, inone or more embodiments or aspects.

Similarly, it should be appreciated that in the description variousfeatures of the invention are sometimes grouped together in a singleembodiment, figure, or description thereof for the purpose ofstreamlining the disclosure and aiding in the understanding of one ormore of the various inventive aspects. This method of disclosure,however, is not to be interpreted as reflecting an intention that theclaimed invention requires more features than are expressly recited ineach claim. Moreover, the description of any individual drawing oraspect should not necessarily be considered to be an embodiment of theinvention. Rather, as the following claims reflect, inventive aspectslie in fewer than all features of a single foregoing disclosedembodiment. Thus, the claims following the detailed description arehereby expressly incorporated into this detailed description, with eachclaim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include somefeatures included in other embodiments, combinations of features ofdifferent embodiments are meant to be within the scope of the invention,and form yet further embodiments, as will be understood by those skilledin the art. For example, in the following claims, any of the claimedembodiments can be used in any combination.

In the description provided herein, numerous specific details are setforth. However, it is understood that embodiments of the invention maybe practised without these specific details. In other instances,well-known methods, structures and techniques have not been shown indetail in order not to obscure an understanding of this description.

In the discussion of the invention, unless stated to the contrary, thedisclosure of alternative values for the upper or lower limit of thepermitted range of a parameter, coupled with an indication that one ofsaid values is more highly preferred than the other, is to be construedas an implied statement that each intermediate value of said parameter,lying between the more preferred and the less preferred of saidalternatives, is itself preferred to said less preferred value and alsoto each value lying between said less preferred value and saidintermediate value.

The use of the term “at least one” may mean only one in certaincircumstances.

The principles of the invention will now be described by a detaileddescription of at least one drawing relating to exemplary features ofthe invention. It is clear that other arrangements can be configuredaccording to the knowledge of persons skilled in the art withoutdeparting from the underlying concept or technical teaching of theinvention, the invention being limited only by the terms of the appendedclaims.

FIG. 1 is a schematic representation of airflow around the rear of aconventional automobile 10. Three upper stream-lines 12 are shownpassing over the top of the vehicle, and three further lowerstream-lines 14 are shown passing underneath the vehicle. Flowseparation occurs for the upper streamlines 12 immediately behind thespoiler 16. Similarly, for the lower streamlines 14, flow separationoccurs immediately behind the rear wheel 18. Accordingly, for themajority of the view shown, laminar flow is spaced substantially awayfrom the vehicle. A relatively large low pressure/turbulent region 20 isshown immediately behind the vehicle and extending between one and twometers away from the rear of the vehicle.

FIG. 2 is a schematic representation of airflow around the rear of theautomobile 10 of FIG. 1 incorporating an active drag-reduction systemthat comprises an upper row of fluid outlets 22 located immediatelybelow the location of the spoiler 16 (which may be removed), a lower rowof fluid outlets 24 located immediately below the bumper/fender 26 andan intermediate row of fluid outlets 28 located on the rear of thevehicle approximately mid-way between the upper 22 and lower 24 rows offluid outlets.

Air ejected from the upper row of fluid outlets 22 draws (e.g. viaBernoulli's principle and/or the Coanda effect) air flow indicated bythe upper stream-lines 12 down such that flow separation is limited.Similarly, air ejected from the lower row of fluid outlets 24 draws airflow indicated by the lower stream-lines 14 upwards, delaying flowseparation.

The air ejected from the upper row 22 is relatively lowpressure/velocity compared to the air ejected from the lower row 24, asthe purpose of the upper row 22 is merely to encourage the Coanda effectaround the spoiler. However, the purpose of the lower row 24 is also tofill the lowest pressure part of the low-pressure/turbulent region 20,thereby artificially raising the pressure and/or overcoming theturbulent flow with artificially introduced laminar flow. Thus the airejected from the lower row 24 is relatively high pressure/velocitycompared to the air ejected from the upper row 22.

Air ejected from the intermediate row 28 is provided to smooth theregion between the upper row 22 and the lower row 24, and is thereforeat a pressure/speed between that of the upper and lower ejected airflows. In smaller cars such as coupes, the intermediate row 28 could bedispensed with. In larger vehicles such as lorries, there may be morethan one intermediate row 28 to allow a more gradual variation ininjected air flow speed/pressure.

FIG. 3 is a schematic representation of an articulated lorry 180incorporating an embodiment of the present invention. The lorry 180,when travelling forwards, suffers from drag, in particular form drag dueto the substantially un-streamlined shape of the vehicle. Vortices 190are formed in a low-pressure region behind the lorry 180, whichcontribute substantially to the form drag. The form drag could bereduces by streamlining the rear of the lorry 180; however, such anapproach is undesirable because of the desire for the vehicle to alloweasy access to its contents. Upper outlets 200 are provided on aperiphery of the rear of the vehicle, and are specifically directed atthe boundary of the vortex behind the vehicle. Intermediate outlets 210are provided on the rear of the vehicle spaced from the periphery, andare specifically directed into the low-pressure region behind thevehicle, in order to minimise drag by reducing vortices and therebyreducing resistance. Lower outlets 200 are also provided. These outletsare preferably nozzles of the form described above. In particular, thefirst outlets may be a convergent nozzles and/or a nozzles supplyingrelatively high temperature air, and the second outlets may be divergentnozzles and/or nozzles supplying relatively low temperature air. Thefigure shows two such outlets of each kind 200, 210; however, a singleoutlet, or multiple outlets (e.g. 3, 4, 5, 6, 10, 20, etc.) of each kindare also envisaged.

In some arrangements, the outlets may be located between the cabin ofthe articulated lorry 180 and the container body, or adjacent to any lowpressure region and/or vortex produced by a similar moving vehicle, suchas behind wheels. In further arrangements, the outlets may be located ona spoiler, or adjacent to a spoiler. In particular, the outletson/adjacent to a spoiler may be convergent nozzles and/or a nozzlessupplying relatively high temperature air. An actuator and forceamplifier assembly may be incorporated (e.g. adjacent to the spoiler),which may receive compressed air at a first pressure and convert it to adifferent pressure in accordance with Pascal's law.

In some embodiments, the nozzle arrangement may be reversed such thatrelatively high temperature air is expelled into a high pressure regionin front of the vehicle, which may be present due to ram forces. Therelatively high temperature air may warm the high pressure region,encouraging it to expand and dissipate, thereby reducing form drag. Inparticular, in some specific embodiments, the nozzles may be directedtoward relatively high pressure regions adjacent to the vehicle.

FIG. 4 is a longitudinal cross section through an outlet of a tip ringnozzle 1, having an annular band 2 located around the interior of theoutlet of the nozzle, the annular band 2 having an approximatelycircular cross section, and being curved around on itself to form asubstantially toroidal shape. The arrow 3 indicated direction of flow ofgas through the divergent part of the nozzle. Preceding parts of thenozzle (for instance, a convergent section) are not shown for clarity.

FIG. 5 is an end on (axial) view of an outlet of an elliptic sharptipped shallow lobed nozzle 4. The nozzle 4 has an interior profile 5 inthe form of four equally spaced lobes, each separated by a sharp wall 6.The inlet 7 of the nozzle 4 is shown as an opening of reduced diameter,which may form the throat of the nozzle. The inlet 7 may comprise theconnection between a converging portion of the nozzle (not shown) andthe diverging portion of the nozzle 4. Therefore, the skilled personwill appreciate that the degree by which the cross section of the nozzlediffers from circular increases from the inlet 7 to the outlet interiorprofile 5.

FIG. 6 is schematic representation of a typical prior art internalcombustion engine and alternator system. An internal combustion engineis provided with a cylinder 1000, a reciprocating piston 2000 therein,an intake 30, an intake valve 40 (for controlling flow of gas into theengine through the intake 1000), an exhaust 50, and an exhaust valve 60(for regulating flow of exhaust gas out of the engine through theexhaust 50).

Operation of the internal combustion engine, the details of which arenot shown for clarity, causes the piston to reciprocate, therebyrotating a crankshaft 70. Rotation of the crankshaft 70 is used to drivea belt 80 which in turn operates alternator 90 via alternator pulley100. The alternator pulley 100 is sized relative to the crankshaft 70such that a higher rpm is provided at the alternator 90 that is presentat the crankshaft 70. That is, the piston 2000 must do work operatingthe alternator 90.

FIG. 7 is a schematic representation of a first embodiment of thepresent invention in which the prior art shown in FIG. 6 is modified inthe following way. A turbine 110 is placed at the exhaust 50 such thatexhaust gases from the engine rotate the turbine. Subsequently, suchgases may leave the turbine via the exhaust outlet 120. The belt 80 iscoupled to an axle of the turbine 110, rather than to the crankshaft 70,thereby reducing the load on the piston 2000. The alternator 90 isdriven by the belt 80, via the alternator pulley 100 as before.

However, the turbine 110 is constructed to provide a rotational speedsuitable for the alternator 90, such that gearing provided by selectingsuitably sized pulleys for use with the belt 80 are not required. In analternative embodiment, it is envisaged that the alternator 90 could beconnected directly to the axle of the turbine 110, foregoing the needfor the belt 80 and alternator pulley 100.

FIG. 8 is a schematic representation of a second embodiment of thepresent invention, which is a further modification of the firstembodiment shown in FIG. 7. In this arrangement, the belt 80 drives thealternator 90 and additionally a further accessory device 130, such asan air conditioning compressor unit. A further accessory device 140 isdriven by a further belt 150, also on the axle of the turbine 110. Thefurther accessory device 140 could be a water pump, for example;however, any other component that would more typically be drivendirectly by the crankshaft.

FIG. 9 is a schematic representation of a third embodiment of thepresent invention, which is an alternative or additional modification ofthe first embodiment shown in FIG. 7. The axle of the turbine 110 ismade in common with an axle of a compressor 160 located at the intake,as is conventional in turbocharging devices. As in the otherembodiments, the alternator 90 is driven by the axle of the turbine 110.A metering valve 170 is located between the compressor 160 and theintake valve 40 and is configured to direct a gas flow from thecompressor away from the intake valve 40, in the event that thecompression provided by the compressor exceeds some threshold amount. Insome embodiments, the diverted gas 180 is conveyed to the exhaust outlet120, or to other outlets such as the propelling nozzles discussed above.The metering valve 170 may divert all or none of the gas from thecompressor 160, or any proportion therebetween.

Although exhaust gas may be conveyed to the propelling nozzles of thepresent invention, it is preferable that exhaust gas is simply expelledin a conventional manner. Gas from another source may be provided to thenozzles. In particular, exhaust gas would be useful because it is bothhot and at relatively high temperature; however, it may also containrelatively large amounts of unburned hydrocarbons and other impurities,which could cause the nozzles to block/clog over time, or at leastreduce their efficiency. It is therefore desirable to use the heatand/or pressure of the exhaust gas to provide suitable air flow throughthe propelling nozzle(s) of the present invention. For example, a heatexchanger could be used to reclaim waste heat, and/or a turbo expandercould be used to extract pressure for re-use. The exhaust gas could thenbe passed to a silencer and/or exhaust pipe exit.

FIG. 10 is a schematic representation of a fourth embodiment of thepresent invention, in which an air compressor 140 is driven by theturbine 110 to produce a stream of compressed air (or other gas) thatflows down a pipe 300. The air compressor 140 may take air from ambient,or in alternative embodiments may take air from the engine inlet viametering valve 170. The compressor may be, for instance, a vane typecompressor.

This air compressed by the air compressor 140 may be supplied directlyto the propelling nozzles and/or may be sent to a vortex tube 310 thatsplits the steam into a relatively high temperature stream that may besent to a propelling nozzle via valve 320 and a relatively lowtemperature stream that may be sent to a propelling nozzle via valve340. Optionally, a heater and/or cooler 330 may be placed in-line witheither the hot stream or the cold stream, or exceptionally to thecompressed air stream prior to its introduction into the vortex tube310. A further check valve 350 may also be included in the pipe 300.Each check valve shown in the drawings may optionally be accompanied orreplaced by a pressure sensor. A controller may be configured to operatethe or each check valve in response to pressure measured by the pressuresensor(s). A fuel control unit may be associated with the or eachpressure sensor and/or check valve.

It is to be appreciated that the arrangement in FIG. 10 could bemodified such that the air compressor 140 is driven by the crankshaft70, rather than via a turbine 110, in a configuration similar to thatshow in FIG. 6.

FIG. 11 is a schematic representation of a fifth embodiment of thepresent invention in which air flow from the metering valve 170(compressed by the compressor 160) is supplied directly to thepropelling nozzles via pipe 360 (conveying relatively cold air), and/orto a heat exchanger 380 via a check valve 370. The heat exchanger 380may be configured to remove heat from the exhaust gases within theexhaust pipe 120 to warm the compressed air from the check valve 370 inorder to provide a relatively high temperature stream 390 to apropelling nozzle, as described above.

FIG. 12 is a schematic representation of a sixth embodiment of thepresent invention in which compressed air is taken from the meteringvalve 170 as in FIG. 11, but is conveyed to a vortex tube 310 as in FIG.10. In particular, a cooler 330 is provided in the pipe 300 prior to thevortex tube 310.

Any combination of the above embodiments may be used to create a systemhaving some or all of the advantages described above.

1. An active drag-reduction system for a vehicle in which at least oneturbulent and/or low-pressure region is formed adjacent to the vehiclewhen moving at a speed above a predetermined threshold speed, the activedrag-reduction system configured to reduce the at least one turbulentand/or low-pressure region when activated, the active drag-reductionsystem comprising: at least one convergent propelling nozzle locatedadjacent to a boundary of the at least one region; at least onedivergent propelling nozzle located adjacent to the at least one regionand spaced from the boundary of the at least one region, the at leastone divergent propelling nozzle arranged to eject fluid substantiallytoward an interior of the at least one region; and a device forproviding gas to each of the at least one convergent and divergentpropelling nozzles for expulsion into the at least one region.
 2. Anactive drag-reduction system for a vehicle in which at least oneturbulent and/or low-pressure region is formed adjacent to the vehiclewhen moving at a speed above a predetermined threshold speed, the activedrag-reduction system configured to reduce the at least one turbulentand/or low-pressure region when activated, the active drag-reductionsystem comprising: at least one propelling nozzle located adjacent tothe at least one region and arranged to eject fluid substantially towardan interior of the at least one region; and a device for providing gasto the at least one nozzle for expulsion into the at least one region;wherein the at least one propelling nozzle comprises a tip ringsupersonic nozzle and/or elliptic sharp tipped shallow lobed nozzle. 3.A method of reducing vehicular drag, the method comprising the steps of:providing a system according to claim 1; and expelling gas from the atleast one nozzle into an interior of the at least one region.
 4. Avehicle configured such that, when moving at a speed above apredetermined threshold speed, at least one turbulent and/orlow-pressure region is formed adjacent to the vehicle, the vehiclecomprising an engine system comprising: an internal combustion enginehaving an intake and an exhaust; a turbine connected to the exhaust suchthat the turbine rotates in response to receiving exhaust gases from theengine; an alternator connected to the turbine such that the alternatorgenerates electrical power in response to rotation of the turbine; andan exhaust outlet connected to the turbine, for removing exhaust gasesthat have been used to rotate the turbine, the exhaust outlet comprisinga propelling nozzle located on a rear of the vehicle such that theexhaust gases are expelled substantially toward an interior of aturbulent and/or low-pressure region behind the vehicle; wherein theexhaust provides gas directly to the nozzle.
 5. A method of reducingvehicular drag, the method comprising the steps of: providing a vehicleaccording to claim 4; and expelling gas from the at least one nozzlesubstantially toward an interior of the at least one region.
 6. Anengine system of a vehicle, the engine system comprising: an internalcombustion engine having an intake and an exhaust; a Pelton wheelturbine of the impulse type connected to the exhaust such that theturbine rotates in response to receiving exhaust gases from the engine;an exhaust outlet to which exhaust gases are delivered after passingthrough the turbine; an alternator connected to the turbine such thatthe alternator generates electrical power in response to rotation of theturbine; a propelling nozzle distinct from the exhaust outlet, thepropelling nozzle arranged to eject fluid substantially toward aninterior of a turbulent and/or low-pressure region behind the vehicle;an air pump connected to the turbine, the air pump configured to take inambient air at a pump inlet and expel pressurised air to the propellingnozzle; and the propelling nozzle configured such that gasses from thepropelling nozzle are converted into a higher speed propelling jet,relative to the speed of the expelled pressurised air from the air pump.7. The engine system of claim 6, wherein the air pump is a reciprocatingpiston compressor.
 8. The engine system of claim 6, wherein thealternator is spaced from the engine by more than 25 cm.
 9. The enginesystem of claim 6, further comprising: a compressor connected to theturbine such that the compressor rotates in response to rotation of theturbine, wherein the compressor is arranged to compress gas for deliveryto the intake; and a metering valve, provided between the compressor andthe intake, configured to regulate the gas pressure provided to theintake.
 10. A method of using energy in exhaust gas from an internalcombustion engine, the method comprising the steps of: providing aninternal combustion engine of a vehicle having an intake and an exhaust;providing a Pelton wheel turbine of the impulse type connected to theexhaust; rotating the turbine in response to receiving exhaust gasesfrom the engine; delivering the exhaust gases to an exhaust outlet afterpassing through the turbine; providing an alternator connected to theturbine; generating electrical power with the alternator in response torotation of the turbine; providing an air pump connected to the turbine;taking in ambient air at a pump inlet of the air pump; providing apropelling nozzle distinct from the exhaust outlet, the propellingnozzle arranged to eject fluid substantially toward an interior of aturbulent and/or low-pressure region behind the vehicle; and expellingpressurised air from the air pump to the propelling nozzle; andconverting the expelled pressurised air from the air pump with thepropelling nozzle into a higher speed propelling jet, relative to thespeed of the expelled pressurised air from the air pump.